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Leap Day Counter

List every February 29 in an inclusive date range.

● Processed locally in your browser
Processed locally in your browser
Leap days Choose an action to process the input.

Processed locally in your browser

Method, example & boundaries

Leap Day Counter: from input to a reviewable result

List every February 29 inside an inclusive start and end date instead of estimating by dividing the year span by four. The explicit list makes century exceptions and partial boundary years visible for schedules, anniversaries, and date-data audits.

Worked example: 2000 through 2024 inclusive

Example input
Start 2000-01-01; end 2024-12-31.
Example output
Seven leap days: 2000, 2004, 2008, 2012, 2016, 2020 and 2024-02-29.

How to interpret it

The year 2000 is included because century years remain leap years when divisible by 400. Both range endpoints include their dates.

Inclusive Gregorian enumeration

The calculator checks candidate years with the divisible-by-4, century, and divisible-by-400 rule, constructs February 29 only for valid leap years, and keeps the date when it lies on or between the supplied endpoints.

Range interpretation

  • Start and end are date-only values; time zones and hours are ignored.
  • The calculation uses the proleptic Gregorian calendar for earlier years.
  • A reversed or invalid range must be corrected before a count is produced.

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